The present invention relates to a method of reacting hydrogen sulfide with an oxygen containing gas for production of sulfur in a Claus sulfur plant More particularly, the present invention relates to such a method in which the hydrogen sulfide is swirled around the oxygen containing gas.
The Claus process is commonly used for recovering suilir from a feed gas stream rich in hydrogen sulfide. A typical Claus sulfur plant comprises a reaction furnace for partially combusting the feed gas stream with an oxygen containing or oxygen enriched gas, a first means of cooling and condensing sulfur from the combustion effluent, at least one train comprising a reheat means, a catalytic Claus reactor and an additional condensing means for further recovering sulfur from the effluent.
Presently known reactors comprise a cylindrical casing into which gas is introduced either axially or tangentially. Air, oxygen enriched air, or oxygen (hereinafter referred to as just oxygen) is introduced into the cylinder generally in the same direction as the gas flow in such a way as to cause mixing of said gas with the air etc. prior to combustion thereof When air and gas are introduced along the axis of the reactor inefficient mixing can result, which causes elements such as ammonia which may be present in the feed gas to be passed therethrough in an unreacted state.
If unreacted ammonia is passed to the downstream catalytic stages it can very rapidly form into ammonia salts such as ammonium sulfide, for example, which tends to block and hence reduce the efficiency of the catalytic stage.
In order to prevent the pass on of unreacted ammonia from the reactor to the catalytic stages it is necessary to ensure that the temperature of the combustion chamber is sufficiently great as to ensure the ammonia is fully destroyed. In order to ensure complete destruction it is necessary to operate with sufficient residence time and with the reactor temperature at least 1,200.degree. C. and preferably between 1,500.degree. C. and 1,650.degree. C. This can be achieved by running the reactor on pure oxygen or oxygen enriched air for example or by splitting the gas flow into two portions and burning the first portion with all of the air required for the Claus reactor and then by introducing the second gas portion of the feed gas into the reactor at a position downstream of this initial combustion zone. This latter method is widely used when more than one feed gas stream is available and where at least one major feed stream contains no ammonia since the second portion of the gas stream must not contain ammonia.
It is an object of the present invention to provide a reactor suitable for use in the Claus process which reduces and possibly eliminates the carry over of unreacted ammonia to the downstream catalytic stages.